This invention relates to high-pressure blowout preventer (BOP) testing in sub surface wells, and more particularly to a multi-gage blowout preventer test joint assembly for testing the variable bore rams against different OD pipe sizes, shear rams, and annular rams in one trip.
In conventional offshore drilling, a subsea wellhead is installed at the sea floor. A riser connects to the wellhead and extends upward to a drilling platform positioned above the water surface. A blowout preventer stack, hereinafter referred to as a BOP, is typically located within the riser.
In order to test the BOP, an operator closes the variable bore rams in the BOP on various diameter drill pipe and applies pressure between the well head plug and the particular variable bore rams being tested. A typical BOP stack contains rams having variable bore ram diameters, so as to engage with for instance 4½″ OD and 6⅝″ OD drill pipe. The BOP system must be capable of sealing off the annular space surrounding the drill pipe and same must be tested per the rig BOP procedure. It is preferred that the BOP test joint assembly be capable of testing the multi-gage pipe diameters in one downhole trip in order to save time and expense of multiple trips in and out of the hole.
One example of a multi-gage BOP test tool is shown in U.S. Pat. No. 6,032,736 issued on Mar. 2, 2000 to Terrell J. Williams. The multi-gage BOP test tool according to the '736 patent is designed to test different size ram and annular BOP's in one trip. The test tool according to that patent has an outer test tool assembly and an inner tube assembly connected in a telescoping relation. The exterior of the outer tube has a plurality of pipe gage diameters corresponding to different drill pipe sizes. A top sub at the top end of the outer tube assembly connects to the drill string and contains an upper seal assembly and stinger. The bottom end of the inner tube assembly is secured to a bottom sub and the bottom end of the outer tube assembly is releasably connected to the bottom sub in the collapsed position. The bottom sub is connected to a test plug and tail pipe assembly and the tool is lowered through the riser pipe and BOP stack to set the test plug in the wellhead. Ram and annular BOPs are tested against a first set of the pipe gage diameters with the tool in its collapsed condition, and then the outer tube assembly is uncoupled from the bottom sub and lifted to its extended position such that another set of the pipe gage diameters are positioned within the BOP stack and the rams and annular BOPs are then tested against the second axially positioned set of corresponding pipe gage diameters. The '736 patent uses a wireline retrievable dart that is dropped down the drill pipe and is held in position in the upper seal assembly. Drilling fluid flow bypasses the upper seal assembly through fluid passageways between the inner and outer tube assemblies and is vented through relief ports at the lower end of the tool.
While the test tool according to the '736 patent works satisfactorily in many environments, it was noted that the use of the wireline retrievable dart presents certain challenges, for instance a possibility that the dart becomes lodged in the well, which can cause loss of time in retrieving the dart. In the present invention, the wireline retrievable dart has been eliminated from the process. The present invention contemplates removal of drawbacks associated with the test tool and for providing a BOP test tool capable of testing different diameter pipes against rams in one trip into the well.